I also own the M&P .22LR and think it's a great addition to the stable along with my M&P .40 full-size and .40 Shields. It probably see's about as much range time (or used to... I'll say why in a minute) if not more than its big brothers as it's just plain fun!
As you eluded to, the M&P .22LRs aren't particularly picky regarding ammo, at least mine isn't. I've probably put well over 5,000 rounds through mine with just about every brand of ammo available and I can count the FTFs on one hand. Of course, because of the generally dirtier .22 rounds it gets a good cleaning after every trip to the range as do all my guns, which I've no doubt helps.
I mentioned it doesn't see as much range time as it used to now. That's because I couldn't resist and bought myself a M&P 15-22 a couple of weeks ago along with adding a few condiments to personalize it. I immediately took it to Doug's to get it sighted in and now I'm like a kid waiting for Christmas; I can't wait for Tuesday evenings to roll around so I can head back to the range to have some more fun with it! I can almost hear the M&P .22 whimpering in its case now it's been bumped out of rotation. But, I digress from the original thread...
Because the M&P .22LR is so easy and comfortable to use, my wife's giving some serious thought to getting into having "fun with a gun" by taking some ladies only lessons, in which case this'll become her range gun... if I can bring myself to giving it up that is.